It is desirable to produce rubber compounds, which include a rubbery polymer(s), exhibiting reduced hysteresis when properly compounded with other ingredients such as reinforcing agents, followed by vulcanization, such rubber compounds being used in tires. The hysteresis of a rubber compound refers to the difference between the energy applied to deform an article made from the rubber compound and the energy released as the rubber compound returns to its initial, undeformed state. In pneumatic tires, lowered hysteresis properties are associated with reduced rolling resistance and heat build-up during operation of the tire. These properties, in turn, result in such desirable characteristics as lowered fuel consumption for vehicles using such tires.
To that end, to alter or manipulate the properties of rubbery polymers, and thus the characteristics of a tire utilizing such rubbery polymer, various modifiers can be incorporated into the rubbery polymer, when that rubbery polymer is compounded, for interacting with reinforcing filler, such as carbon black or silica. For example, it is known to incorporate tin coupling agents, such as tin tetrachloride, i.e., SnCl4, into rubbery polymers in an effort to improve the performance characteristics of tires. However, it would be desirable to increase the bound rubber by maximizing the number of carbon-tin bonds and, thus, further improve upon the performance characteristics of tires. However, due to the unpredictable interactions of the various compounds and chemicals used for synthesizing and compounding rubbery polymers, it can be challenging to formulate useful rubber compounds that provide tires with overall desirable performance characteristics.
It would thus be desirable to provide rubbery polymers containing tin coupling agents and rubber compounds including the same for use in tires, wherein such rubbery polymers can provide desirable dispersion of reinforcing filler and desirable wear properties.